The present invention relates to a filter arrangement of a vehicle. Concerning the state of the art, reference is made to German patent document DE 10 2006 027 572 A1.
To obtain marketing authorization for a vehicle, specific test cycles have to be driven, for example, to prove that the hydrocarbon emission limit values are maintained. So that no hydrocarbons are released into the atmosphere, an activated carbon filter is disposed between the tank and the atmosphere in the case of motor vehicles having an Otto engine. This activated carbon filter absorbs the gaseous hydrocarbons from the tank ventilation system. However, the activated carbon filter has to be regenerated on a regular basis. The regeneration takes place by way of the internal-combustion engine driving the vehicle, which internal-combustion engine generates a vacuum and can thereby take in air from the environment through the activated carbon filter. In this case, the previously stored hydrocarbons separate from the activated carbon filter and, together with the ambient air, arrive in the internal-combustion engine, where they are burned. However, this quasi external source of hydrocarbons is an “interference” for the engine, and its influence or effect on the internal-combustion engine therefore has to be predicted as accurately as possible, in order to mutually adapt the taken-in quantity and the normal injection of gasoline. During the regeneration of the activated carbon filter, the hydrocarbon concentration in the scavenging air, i.e. in the air stream taken in by the internal-combustion engine through the activated carbon filter, will also fluctuate. This concentration in the scavenging air is, among other factors, a function of the volumetric efficiency of the activated carbon filter.
In the initially mentioned document, a method and a device are described for determining the loading of a fuel vapor temporary storage device in the case of internal-combustion engines, in which case the above-mentioned volumetric efficiency is determined from the vibration behavior of the activated carbon filter. For this purpose, the activated carbon filter is swingably suspended by way of two spring elements with a degree of freedom in the gravitational direction of the earth, although the schematic diagram of this document does not clearly indicate how this suspension is concretely implemented. However, it is clearly shown that the activated carbon filter in the area of a right side of its housing and in the area of a left side of its housing is in each case swingably suspended by way of a spring element in the gravitational field of the earth.
The above-described known spring-mounted suspension may, however, result in undefined or not clearly analyzable vibrations, particularly when the right-side and the left-side spring elements are expanded to different degrees.
It is an object of the present invention to provide a filter arrangement of a vehicle in which only unambiguous and therefore clearly analyzable vibrations or vibrating motions of the activated carbon filter can occur.
This and other objects are achieved by a filter arrangement of a vehicle, particularly a motor vehicle, comprising a filter. In particular, the filter is an activated carbon filter for filtering hydrocarbons in the waste air of a tank of the vehicle. By way of the following description, it will, however, be demonstrated that the invention, especially the weighing of the filter and the determination of the volumetric efficiency of the filter based on the weight, can also be applied to additional filters in a motor vehicle, for example, to dust filters and the like. Furthermore, the filter arrangement according to the invention comprises a spring-mounted suspension of the filter in the vehicle such that the filter is suspended swingably about a vehicle-fixed axis of rotation. Furthermore, a sensor unit is provided which is designed for determining the weight of the filter. In this case, the term “weight” is synonymous with the term “mass”.
In addition, an analyzing unit is provided. The empty weight of the filter can be stored in the analyzing unit. The analyzing unit is designed for calculating the filling degree of the filter. This calculation takes place on the basis of the empty weight and the determined weight. In this case, the empty weight is subtracted from the determined weight, in order to obtain the weight of the charge of the filter. The weight of the charge of the filter corresponds to the “filling degree”. Based on the calculated filling degree of the filter, further steps can be initiated in the vehicle. It is therefore, for example, contemplated, as described in the following, to appropriately actuate the internal-combustion engine as well as the normal valves of the tank ventilation system of the vehicle based on the calculated filling degree. In addition, for example, a status message or a fault report can be emitted in the vehicle when a defined filling degree has been reached.
The sensor unit is designed for measuring a vibration of the filter, the filter being able to vibrate only in a single possible defined fashion, specifically about an axis of rotation, with respect to which the filter is suspended or disposed in a swingable manner. The measurement by the sensor unit thereby supplies an unambiguous correct result. Based on the measured vibration, advantageously the natural frequency of the spring-mass system formed by the filter as well as a suitable spring element is determined, by way of which spring element, the filter is appropriately supported. Based on the natural frequency, in turn, the weight of the filter can be calculated, because the natural frequency is inversely proportional to the square root of the mass (weight).
It is further provided that the sensor unit comprises a sensor. This sensor is used for measuring the vibration of the filter. A magnetic coil sensor, for example, is provided as a sensor, which is correspondingly connected with the filter or the spring-mounted suspension of the filter. As an alternative, the vibration can be measured by use of an optical sensor.
The vibration of the filter can be caused by the natural movement of the vehicle. As an alternative or in addition, a targeted vibration stimulation can take place by use of an actuator. The function of the actuator of the sensor unit may preferably be integrated in the magnetic coil sensor. Thus, by correspondingly actuating the coil, the magnetic coil sensor can be used not only for measuring the vibration but also for stimulating the filter. The magnetic coil sensor has an advantage over an optical sensor in that the magnetic coil sensor can be used as an actuator. In view of a vibration stimulation for the filter by the vehicle itself, i.e. as a result of its movement, which also for energy-related reasons is particularly advantageous, a swingable suspension of the filter, specifically in a rotatable or swingable manner about a vehicle-fixed axis of rotation, is also particularly advantageous. By means of the suggested arrangement, the filter will then be caused to move in the case of each significant acceleration operation and braking operation, when the axis of rotation extends in the direction of the transverse vehicle axle (and at least approximately parallel to the ground). In this sense, the invention also includes a vehicle having a filter arrangement according to the invention, wherein the sensor unit and/or the analyzing unit is/are designed for determining the actual weight of the filter while the vehicle is at least approximately stopped, the vibrating motion of the filter being a result of a preceding braking operation of the vehicle. The risk of faults as a result of a new vibration stimulation because of a changed vehicle movement is thereby minimized.
Facultatively, the same also applies to an alternative arrangement of the filter according to the invention in the vehicle, specifically when the above-mentioned axis of rotation extends essentially in the direction of the vertical axis of the vehicle (and therefore at least approximately perpendicularly with respect to the ground). The filter will then be caused to move in the case of any significant yaw movement (cornering) of the vehicle. In contrast, in the case of a filter arrangement according to the initially mentioned state of the art, only vertical (actually undesirable on the part of the vehicle occupants) vibrations of the vehicle body may cause a vibration stimulation of the filter.
The invention further includes a vehicle having a filter arrangement according to the invention, wherein the filter is designed for filtering waste air, which originates from the fuel tank of the vehicle. This particularly relates to a vehicle having an Otto engine, wherein the filter is constructed as an activated carbon filter for filtering hydrocarbons. The filter in the vehicle is advantageously connected with the tank by way of a corresponding pipe. An additional pipe connects the filter with the vehicle internal-combustion engine. Furthermore, the filter is connected with the atmosphere.
It is preferably provided that the internal-combustion engine of the vehicle is designed for regenerating the filter. For this regeneration operation, the engine is correspondingly actuated for taking in air by way of the filter. In the process, the hydrocarbons will then separate in the filter and burn in the engine. Advantageously, an engine control unit is provided which can correspondingly actuate the engine in order to take in air by way of the filter and inject the correct amount of fuel. As a result of the calculation of the filling degree of the filter, this regeneration of the filter can be carried out in a precise manner, if required. For this purpose, the actuation of the engine takes place as a function of the calculated filling degree.
Furthermore, a method of operating the described filter arrangement and for operating the described vehicle, respectively, is provided. In this case, a determination of the weight of the filter and a calculation of the filling degree of the filter take place according to an advantageous further development from a calibrating step for determining the empty weight of the filter. Thus, within the scope of the method, it is provided in particular that the vibration of the filter is measured, and based on the vibration, the natural frequency is calculated. Based on the natural frequency, the weight of the filter is calculated. Furthermore, a process step for calibrating the system is provided. When calibrating the system, a determination of the weight takes place directly after a long phase of regeneration, thus, the taking-in of air by the engine. This weight is stored and is taken into account in the subsequent calculations of the filling degree. In particular, the weight determined directly after the regeneration of the filter, is stored as “empty weight”.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.